The present invention relates in general to data processing networks, and in particular to a bridge utilized to couple a plurality of local area networks.
There are many different types of networks and network systems for sharing files and resources or for otherwise enabling communication between two or more computers. The term xe2x80x9cnetwork devicexe2x80x9d generally refers to a computer linked to a network via a network interface card (NIC), or to other devices that perform specialized functions in the network, such as repeaters or hubs, bridges, switches, routers and brouters, to name a few examples. Networks may be categorized based on various features and functions, such as message capacity, range over which nodes are distributed, node or computer types, node relationships, topology or logical and/or physical layout, architecture or structure based on cable type and data packet format, access possibilities, etc. For example, the range of a network refers to the distance over which nodes are distributed, such as local-area networks (LAN) within an office or floor of a building, wide-area networks (WANs) spanning across a college campus, or a city or a state and global-area networks (GANs) spanning across national boundaries.
A network may be expanded by using one or more repeaters, bridges, switches or similar type devices. A repeater is a device that moves all packets from one network segment to another by regenerating, re-timing, and amplifying the electrical signals. A bridge is a device that operates at the Data-Link Layer of the OSI (Open Systems Interconnection) Reference Model and passes packets from one network to another and increases efficiency by filtering packets to reduce the amount of unnecessary packet propagation on each network segment. A switch is a network device similar in function to a multiple port bridge, but includes a plurality of ports for coupling to several similar networks for directing network traffic among the networks.
Some bridging devices, such as multiple port bridges, switches, routers or the like include the capability for a user to define one or more Virtual LANs (VLANs). Separate VLANs enable separate address space to be associated with each VLAN. The user or network administrator defines one or more VLANs by grouping one or more ports together in a VLAN definition, where the bridging device effectively separates each VLAN from the other ports. Bridging devices which are VLAN-capable forward traffic amongst ports which are members of the same VLAN.
Within a bridge, it is often desired to monitor the performance of the bridge using various statistics. Bridge statistics are also useful in diagnosing network problems. Standard-based statistics defined for traditional 802.1D bridges and defined in RFC 2674 (xe2x80x9cDefinitions of Managed Objects for Bridges with Traffic Classes, Multicast Filtering and Virtual LAN Extensionsxe2x80x9d) are inadequate to describe the number of frames forwarded or discarded for IEEE 802.1Q VLAN bridges. In the traditional bridge model described in IEEE 802.1D the number of frames forwarded by a bridge port can be deduced from the number of frames received and the number of frames discarded on that particular port by the forwarding process. As illustrated in FIG. 3, there was only a single simple forwarding process implemented within the 802.1D bridge 301 coupling LANs 302 and 303. Frames are received from LAN 302 into port 1 by frame reception 304, and then sent to forwarding process 305, which will perform a filtering process as a function of filtering parameters from filtering database 306. This filtering, or discarding, of frames in the forwarding process 305 is performed with respect to one or more filtering rules, which are described within the 802.1D specification. As a result, the number of frames forwarded from port 1 will equal the number of frames sent from frame reception 304 to forwarding process 305 minus the number of frames filtered, or discarded, within forwarding process 305. Then, the number of frames transmitted from frame transmission 307 to port 2 will equal the sum of all frames forwarded to the transmitting port 307 from the forwarding process 305.
However, as will be described herein, the new 802.1Q-based bridge model is considerably more complicated, and therefore the standards-based statistics implemented within the traditional 802.1D bridge 301 are inadequate.
The present invention addresses the foregoing need by implementing counters within a bridge so that adequate forwarding and transmission statistics can be monitored. The counting of frame discards as a result of ingress rules implemented within the bridge, and as a result of egress rules implemented within the bridge, are utilized within the 802.1Q VLAN bridge model to calculate the number of frames forwarded and the number of frames transmitted.
The additional counters serve two functions. The first function is to completely identify the number of frames received on a bridge port and actually forwarded to other bridge ports. This is provided by taking into account the number of frames that are received on a bridge port, but subsequently discarded because of ingress rules, as defined by IEEE 802.1Q. The number of frames forwarded from the bridge port is calculated as the number of frames received on a bridge port minus the number of frames discarded for any of the following reasons:
1. The forwarding process of the bridge mandates that the frame be discarded;
2. The frame has an unacceptable frame type (i.e., is incompatible with the acceptable frame types parameter configured for the bridge port);
3. The frame fails the ingress filtering rule configured for the bridge port; or
4. Other VLAN-related reasons mandate discarding the frame (i.e., no VLAN registration exists on the bridge for the VLAN ID carried within the frame).
The second function of the additional counters is to identify the number of frames submitted for transmission from a bridge port. This number is a subset of the number of frames forwarded to a bridge port from all other ports. This value is provided by taking into account the number of frames that are discarded because of egress rules, as identified by IEEE 802.1Q. This number can be derived from the number of frames forwarded to the bridge port from all other ports minus the number of frames discarded for any of the following reasons.
1. The port is not a member of the VLAN with which the frame is associated; or
2. The port is configured to transmit frames as untagged, and the frame""s VLAN tag indicates the presence of embedded MAC addresses which cannot be translated into a format compatible with the local media with which the port is associated.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.